This bulletin applies to a number of GM vehicles including 2000-2004 Chevy Malibu, 2000-2004 Buick Century, 2000-2004 Buick Rendezvous, 2000-2004 Chevy Impala, Monte Carlo and Venture, 2000-2004 Olds Alero and Silhouette, 2000-2004 Pontiac Aztek, Grand Am, Grand Prix and Montana models. If the engine exhibits a misfire at a steady speed and rpm, with DTC P0300 set, there’s a good chance that the fuel injector connectors are crossed.
If the fuel injector harness has been off previously, remove the manifold and check the color code of each circuit to verify that it’s routed to the correct injector.
The rear cylinder head is the odd bank (1-3-5) and the front head is the even bank (2-4-6). The numbers cast into the intake manifold make it look opposite because the runners cross to the opposite side.